Calling the invalidation function during initialisation of the data
stores introduces a circular dependency, causing Synapse to fail to
start.

This is so that we don't have to rely on pulling it out from `current_state_events` table.

Currently if a worker invalidates a cache it will be streamed to master, which then didn't forward those to other workers.

Clarifications to the workers documentation

Co-Authored-By: Brendan Abolivier <babolivier@matrix.org>

Signed-off-by: Jason Robinson <jasonr@matrix.org>

* Add note that user_dir requires disabling user dir
  updates from the main synapse process.
* Add note that federation_reader should have
  the federation listener resource.

Signed-off-by: Jason Robinson <jasonr@matrix.org>

There are quite a few places that we assume that a redaction event has a
corresponding `redacts` key, which is not always the case. So lets
cheekily make it so that event.redacts just returns None instead.

* a bit of debugging for media storage providers

* changelog

* don't insist on a password (this is valid if you have an SSO login)
* fix reference to undefined `requester`

Fix typo in _select_thumbnail

These now exist in the pipelines repo.

The old statement returned `None` for such a `password_config` (like the one
created on first run), thus retrieval of the `pepper` key failed with
`AttributeError`.

Fixes #5315

Signed-off-by: Ivan Vilata i Balaguer <ivan@selidor.net>

* Raise an exception if there are pending background updates

So we return with a non-0 code

* Changelog

* Port synapse_port_db to async/await

* Port update_database to async/await

* Add version string to mocked homeservers

* Remove unused imports

* Convert overseen bits to async/await

* Fixup logging contexts

* Fix imports

* Add a way to print an error without raising an exception

* Incorporate review